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I'm trying to record voice from a microphone into my laptop. Unfortunately, the laptop does not have a microphone jack, so I have to use the USB input. This doesn't present a problem when I record voice from my gaming headset, but when I record from the condenser microphone over USB I get a very pronounced line hum. This occurs even when the laptop is unplugged from power and on its battery.

The hum consists mainly of 55 Hz noise, but with some 110 and 512 Hz components. I can eliminate this using a notch filter in "post production", as it were, but I'd rather not have to do this. This noise is not the fault of the microphone, by the way (at least not directly), since when I run the microphone signal into my digital voice recorder (using a 3.5mm plug) there is no background hum at all.

Is there some way to process or filter the output from the microphone so that this noise never makes it to the laptop?

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  • $\begingroup$ How do you digitalize your signal to send it over USB ? I find it unclear as you stated that you used the same microphone using an analog 3.5mm jack and a digital USB. $\endgroup$ Jan 7 '17 at 3:39
  • $\begingroup$ @Pier-YvesLessard, the microphone has XLR output, and I can attach either an XLR to USB cable or an XLR to 3.5mm cable to it. I'm getting the hum with USB on the laptop -- but the laptop doesn't have a mic input. When I use the 3.5mm cable into a digital voice recorder there is no hum. $\endgroup$ Jan 12 '17 at 10:03
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I would suggest adding a device as like Xenyx 302USB (~50$) in your recording path.

If it's just voice recording in question (and Windows based computer) then you could install EqualizerAPO and prepare suitable filters for to fix the issue. Maybe one steep (something like 72dB/oct or even steeper) HPF to cut below 75Hz-80Hz frequencies or bandpass filter (by this article) could work but, with setting few notch type filters by the hum frequencies your hum issue certainly can be fixed. EqualizerAPO allows you to set the filters work for recording device as well as for the playback device.

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You already know the noise frequencies, if you know the phases, you can cancel the noise by adding mods with opposite phase, like adaptive headphones do.

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  • $\begingroup$ This only works if you have very good estimates of not only frequency and phase but also the amplitude of the hum tones. And I think these could be difficult to obtain in this scenario. If your estimates deviate too far from the true values - which may even fluctuate - you risk exacerbating the problem dramatically and making the hum louder instead of reducing it. $\endgroup$
    – applesoup
    Jun 6 '17 at 23:13
  • $\begingroup$ Thank you for the comment. But adaptive headphones does this job pretty good. $\endgroup$ Jun 8 '17 at 0:36
  • $\begingroup$ Interesting thought. It's trivial to duplicate the track and invert the phase. $\endgroup$
    – stephen
    Feb 5 '19 at 7:36
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it's super hard to say for sure what is causing the noise, however you could try changing a few things.

Try turning off microphone boost, this can be found in your 'recording devices', under your mics 'properties'.

From the same menu, you could also try a different volume, try turning your mic down a little from this menu.

the software you are using might be using an 'automatic voice gain detection' setting, turn this off to avoid the microphone increasing its sensitivity automatically. Justheadphone

Even trying a different USB port could be useful, as some of the noise is very possible electronic interference fro your USB port, this will be almost impossible to eliminate.

and finally, and probably the hardest one to test. Try a different environment, or even perhaps try and add some sound proofing to your current environment.

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